Not Applicable.
Not Applicable.
This invention relates generally to the detection of obstruction of power-operated doors when closing, so that if obstruction is detected the closing can be discontinued. More particularly the invention relates to the testing of the operational condition of such a system, with the object of ensuring that it functions satisfactorily when required.
The invention has been devised in relation to doors for use on passenger carrying public service vehicles (buses and coaches) although it will be appreciated that it may be of broader application wherever power-operated doors are utilized e.g. in industrial applications. It is known to provide an edge of a power-operated door, which edge is the leading edge when the door is closing, with a means for detecting an obstruction if one is encountered in the course of closing of the door, for giving a signal so that closing of the door can be discontinued to prevent damage from occurring if attempted closing of the door against the obstruction is continued or injury if the obstruction is caused by a person. Such a system, a so called xe2x80x9csensitive edgexe2x80x9d system using electrical sensors at the door edge is known and also it is known to have a pneumatically-operating sensitive edge system. In the latter, a sensing element comprising a flexible air chamber carried at the edge of the door is compressed if an obstruction is encountered causing a pressure rise in the interior of the chamber which can be detected and to which a control system can respond by discontinuing closing of the door. Since doors on transport vehicles commonly are pneumatically operated, the use of such a pneumatic sensitive edge system is convenient.
However such a pneumatic sensitive edge system will not work if the air chamber provided along the edge of the door, or the connections thereto or associated therewith, become damaged. The present invention relates to the detection of any such damage which might cause the sensitive edge system to malfunction, and broadly it is the object of the present invention to provide an improved means for detecting such damage.
According to one aspect of the present invention, we provide a method of testing the integrity of a fluid-pressure-responsive sensing element for an obstruction-detection system, comprising applying to the interior of the sensing element a predetermined change in pressure; providing for relief of said changed pressure in a predetermined manner; and assessing a characteristic of the manner in which the pressure is actually relieved to provide, in comparison with said predetermined manner, an indication of said integrity.
Preferably said predetermined change in pressure is a pulse of increased pressure, applied by introducing a small quantity of fluid into the sensing element.
Preferably said relief of pressure in a predetermined manner is provided for by arranging for leakage of fluid from the sensing element by way of a small bleed orifice connecting the interior of the sensing element to external atmosphere, the size of the orifice being selected to provide a controlled rate of leakage of fluid from the sensing element.
Preferably the characteristic which is assessed is the rate at which pressure in the sensing element changes in response to the pressure pulse applied thereto, and this is most conveniently measured by timing the duration of the pressure pulse. Such timing may be effected by measuring the time elapsing between the pressure falling from a first value to a second value or rising and falling between said values.
If the sensing element is damaged and leaking, the pressure pulse applied thereto will diminish more rapidly than it would if the only source of leakage were the bleed orifice. If there were any blockage for example in a flexible pipe leading to a sensing element on the edge of a door, the result will be a pulse of longer duration than normal. Detection of a longer or shorter pulse than normal may then be used to cause a fault signal to be given. Whether the fault results from damage or obstruction in the sending element or pipes leading thereto, or a fault in the pulse generator itself, detection of the fault indicates the need for repair to be carried out.
Preferably testing of the sensing element as aforesaid is carried out each time a powered door provided with the sensing element is opened.
According to another aspect of the invention, we provide an obstruction detection system including a fluid-pressure-responsive sensing element and means for testing the integrity of said sensing element and associated parts of the system. The testing means comprises means for applying a predetermined change in pressure to the interior of the sensing element; means providing for relief of the changed pressure in a predetermined manner; and means for assessing the manner in which the pressure is actually relieved to provide, in comparison with the predetermined manner, an indication of said integrity. Preferably, the means for applying a predetermined change in pressure to the interior of the sensing element comprises means for creating a pressure pulse in said sensing element by introducing a predetermined quantity of fluid into the sensing element. A bleed orifice may provide for relief of excess pressure in the sensing element in the predetermined manner. In a preferred embodiment, the pressure pulse generating means comprises a piston movable within a cylinder, conveniently in response to the application of fluid pressure to the cylinder space on one side of the piston, with the cylinder space on the other side of the piston being connected to the sensing element. A one-way valve may be provided between the cylinder space on the other side of the piston and a connection leading to the sensing element.
As applied to a pneumatically operated door system, the obstruction detection system may be caused to operate each time the door is opened. The air pressure which causes the piston to be displaced to apply the pressure pulse may be caused to be applied by a control valve which causes the door to be opened, so that the pulse is provided each time the door is opened.
Preferably the characteristics of the pulse to indicate the integrity of the system are assessed by a pressure sensor providing an electrical output signal which is analyzed by a microprocessor-based data processor. It will be appreciated that in an obstruction detection system using a pneumatic sensing element, there is in any event provided a means for detecting when an obstruction is encountered by responding to the increase in system pressure caused thereby: in a system in accordance with the present invention the additional means for assessing the characteristics of the pressure pulse may be added to such a pressure sensor and data processing device. Preferably the characteristic which is assessed is the duration of the pressure pulse, as explained above and hereafter.
Various objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings.